r255524 - clang-cl: make /Wall turn on both -Wall and -Wextra (PR25563)

[Hans Wennborg via cfe-commits]

On Mon, Dec 14, 2015 at 3:47 PM, David Blaikie via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> On Tue, Dec 15, 2015 at 5:46 AM, Hans Wennborg via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
>>
>> Author: hans
>> Date: Mon Dec 14 12:46:11 2015
>> New Revision: 255524
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=255524&view=rev
>> Log:
>> clang-cl: make /Wall turn on both -Wall and -Wextra (PR25563)
>>
>> The documentation suggests /Wall should really turn on -Wextra and any
>> other warnings that are not enabled by default. That would correspond
>> to Clang's -Weverything, but is probably not what users want.
>
>
> I'd be hesitant to water down an "enable all the warnings, including new
> ones added in future compiler releases" like this... it seems a pretty
> significant feature for users and to have the switch to LLVM stagnate their
> warning bar when they were trying to do something more like -Weverything
> (opt into everything, disable whatever is undesirable) might be unfortunate
> for users.

I looked at the list of the MSVC warnings not enabled by default [1],
and those are all reasonable warnings the we'll turn on under -Wall
-Wextra in Clang. I think that's what MSVC users using /Wall wants,
and the comment on the PR seems to match that.

I don't think any user actually wants *everything* (e.g.
-Wmissing-prototypes) - I almost think of it as an internal flag
mostly useful for Clang development. If the user really wants it, she
can do "clang-cl -Weverything".

  1. https://msdn.microsoft.com/en-us/library/23k5d385.aspx